In a variety of industrial and commercial settings it is necessary or desirable to provide soil drainage to remove unwanted water. For example, in agriculture fields or golf courses, low spots frequently are drained to prevent accumulation of excess moisture which, in the case of agricultural fields would inhibit crop growth and yields, and in the case of golf courses, would provide unsuitable playing conditions.
Road construction is another significant example. Moisture immediately beneath the pavement surface causes distresses of varying types which may rapidly destroy the pavement. In flexible pavement systems, distresses may be caused by either water alone or in combination with temperature variations. Such distresses include pot holes, loss of aggregates, raveling, weathering, alligator cracking, reflective cracking, shrinkage cracking, and heaving from repeated frost/thaw cycles and/or swelling soils. Rigid pavement systems distresses include faulting, joint failure, pumping, various types of cracking, blow-up or buckling, surface spalling, steel corrosion, and heaving from frost/thaw and/or swelling soils. These distresses are discussed in more detail in U.S. Pat. No. 4,572,700.
A variety of drainage systems have been employed over the years in attempts to provide economical drainage systems to accomplish desired drainage objectives. Early drainage systems comprised filling trenches with sand and coarse aggregates in place of indigenous soils less permeable to water, such as clay. An improvement on these systems utilized synthetic textile fabrics (geo-textiles) as a trench liner, filled with a coarse aggregate to support the fabric. Geo-textiles prevent the aggregate from clogging with silt, thereby defining a drainage passageway. More recently, round perforated corrugated tubing has been used, typically placed in an aggregate-filled trench, sometimes in combination with a geo-textile covering the perforated conduit. See, e.g., U.S. Pat. Nos. 3,830,373; 4,182,591; and 4,572,700.
As discussed in detail in U.S. Pat. No. 4,572,700, many of these prior art drainage systems are relatively expensive to install due to being labor-intensive, and/or requiring removal and replacement of relatively large volumes of indigenous soil with preferred aggregate and/or sand backfill, processes involving extensive transportation of soil and backfill. Other products, such as the drain strips shown in U.S. Pat. Nos. 4,639,165 and 4,572,700, intended to be less costly to install, are relatively fragile in their construction, and tend to not support the filter fabric adequately against soil pressures, particularly during backfilling.
U.S. Pat. No. 4,995,759 proposed a drainage tube construction falling in the class generally designated as "edge-type" drainage systems. This construction consists of several longitudinally extending parallel corrugated plastic (typically, e.g., polyethylene) tubes stacked upon one another to form a relatively tall, elongated edge drain product that is relatively narrow (in transverse cross-section), permitting it to be installed in relatively narrow trenches. This system (along with other relatively narrow edge-type drainage products) reduce the amount of indigenous soil which must be removed and the amount of backfill utilized in installing a drainage system.
While the drainage tube construction of U.S. Pat. No. 4,995,759, along with other edge-type drainage systems, can be manufactured relatively economically, it has been found that actual installations of such products desirably require a variety of different types of junctions between adjoining lengths of tubing. Each junction of a different type therefore requires the manufacture of a specialized fitting designed particularly for that type of junction. With a wide variety of possible types of drainage tubing installation configurations, a need has arisen for a wide variety of junction fittings. The cost of manufacturing molds for each type of fitting, however, can be significant-the unit volume demand for any one particular fitting is substantially less than demand for the drainage product itself, resulting in a relatively high per unit cost for the fittings in relation to the cost of the tubing. Moreover, as more applications for edge drain-type products are found, specialized fittings to facilitate such applications are often necessary. The economic viability of manufacture of such variety of fittings, however, poses a significant limit on the range of possible applications.
Accordingly, there is a need for an economical system of fittings for use with edge-type drain products generally, and for the particular edge-type drain product described in U.S. Pat. No. 4,995,759.